Evolution of the colour-pattern and orthogenetic variation in certain mexican species of lizards, with adaptation to their surroundings

The late Th. Eimer has shown that the variations of the colour-pattern of the EuropeanLacerta muralis proceed each on definite lines until a certain stage is attained which is characteristic of the race, or variety, in question. This mode of development he has termedorthogenetic . As a rule, the successive changes in the colour-pattern of lizards, are as follows: First longitudinal stripes, then dissolution of the stripes into spots, then confluence of the spots in a transverse direction so that a cross-barred pattern is produced, lastly a uni-coloured appearance. There are some lizards which pass through the whole scale during their growth from youth to old age. Others again stop short at perhaps the second, or even at the first stage.